1. Field of the Invention
This application is based upon and claims the benefit of the priority of Japanese patent application No. 2011-054944, filed on Mar. 14, 2011, the disclosure of which is incorporated herein in its entirety by reference thereto.
The present invention relates to a semiconductor device having a memory cell.
2. Description of Related Art
In a semiconductor device such as a DRAM (Dynamic Random Access Memory), due to miniaturization of processing sizes, i.e., decrease in bit line pitch and word line pitch, trench gate structure in which a gate electrode is embedded in a Si substrate is employed in order to reduce off-current of a memory cell selecting transistor.
Further, as a method for controlling a word line in a DRAM, in order to prevent a current load of a negative potential power supply from increasing due to a reset current to a word line, a method is known, in which once a word line potential is discharged to an intermediate potential such as a ground potential at a time of resetting the word line and then the word line potential is discharged to a negative potential, which is the reset potential (for instance, refer to Patent Documents 1 to 10).    [Patent Document 1]    Japanese Patent Kokai Publication No. JP-A-H05-89673, which corresponds to U.S. Pat. No. 5,297,104.    [Patent Document 2]    Japanese Patent Kokai Publication No. JP-A-H10-241361, which corresponds to U.S. Pat. No. 6,046,956.    [Patent Document 3]    Japanese Patent Kokai Publication No. JP-A-H11-31384    [Patent Document 4]    Japanese Patent Kokai Publication No. JP-A-H11-328953    [Patent Document 5]    Japanese Patent Kokai Publication No. JP2001-126473A, which corresponds to U.S. Pat. No. 6,262,934B1.    [Patent Document 6]    Japanese Patent Kokai Publication No. JP2002-352580A, which corresponds to U.S. Pat. No. 6,545,923B2.    [Patent Document 7]    Japanese Patent Kohyo Publication No. JP2007-504594A, which corresponds to U.S. Pat. No. 7,839,701B2, U.S. Pat. No. 7,324,390B2 and U.S. Pat. No. 7,082,048B2.    [Patent Document 8]    Japanese Patent Kokai Publication No. JP2010-67337A, which corresponds to US2010/061175A1.    [Patent Document 9]    Japanese Patent Kokai Publication No. JP2000-36191A    [Patent Document 10]    Japanese Patent Kokai Publication No. JP2003-30984A, which corresponds to U.S. Pat. No. 6,661,734B2.